Certain medical conditions or diseases require that patients intermittently inject a drug or therapeutic agent subcutaneously to maintain the medical condition or disease under control. Multiple daily injections (MDIs) may be required. One such medical condition is diabetes, for which insulin is injected to regulate blood glucose. An estimated twenty-six million people in the United States, or about 8% of the population, have diabetes. This percentage is expected to increase in the near-term as the population ages.
To achieve better control over blood sugar levels, basal-bolus therapy is often recommended for people with Type 1 or Type 2 diabetes. Basal-bolus insulin therapy is delivered either through multiple daily injections (MDIs) or through insulin pump therapy. The goal of basal-bolus therapy is to mimic the way blood sugar is controlled naturally.
Multiple daily injections use an insulin pen or a syringe and require the use of two different insulin types for bolus and basal therapy. Long acting insulin, or basal insulin, begins working in 1-2 hours but is slowly released so it can last up to 24 hours to keep blood glucose levels at consistent levels during periods of fasting. Rapid acting insulin, or bolus insulin, is specifically taken at meal times to keep blood sugar levels under control following a meal.
Insulin pump therapy uses an insulin pump and requires only a single type of insulin (usually rapid acting) that is delivered during a meal as a bolus injection, and slowly and continuously throughout the day as basal injections.
Unfortunately, both MDI and insulin pump therapy present problems for patients in implementing basal-bolus therapy. For MDI, certain patients are unlikely or unable to follow the drug regimen required to maintain their medical condition under control. Some patients are squeamish about injecting the drug themselves and others suffer adverse effects from repeated injections, such as bruising at the injection site. Mechanical insulin pens are large and bulky, discouraging the patient from using them regularly. Use of the mechanical insulin pen is also indiscreet.
For insulin pump therapy, delivering fluid continuously and accurately over long periods of time generally requires an electromechanical device to perform and control the pumping. This adds cost and size to the insulin pump due to the pumping actuator itself as well as the required battery and electronics. Many patients are unwilling or unable to use dedicated electronic insulin pumps due to the expense, complication, and obtrusiveness.
It would be desirable to have a mechanical injection pump and method of use that would overcome the above disadvantages.